1. Field of the Invention
The present invention relates to use of molecular weight-enlarged ligands and catalysts in a process for the asymmetric, continuous catalytic hydrogenation of Cxe2x95x90C, Cxe2x95x90N or Cxe2x95x90O double bonds. This process is particularly suitable for continuous processes performed in a xe2x80x9cmembranexe2x80x9d reactor. The present invention also relates to molecular weight-enlarged catalysts and processes of making same.
2. Discussion of the Background
Continuous processes are highly preferred at the large industrial scale. In order to save on process costs, catalytically based processes are becoming more widely used in industry. Continuous catalytic processes are difficult to carry out because of the associated problems such as, for example, separability of the product from the catalyst, inactivation of the catalyst over time, and the development of suitable catalysts.
Recent attempts to overcome the above-mentioned problems include the separation of molecular weight-enlarged, homogeneously soluble catalysts from low molecular weight products by nano- and ultrafiltration membranes. Molecular weight-enlarged catalysts for homogeneous enantioselective hydrogenation are described, for example, in U.S. Pat. No. 5,777,062, which also describes the separation thereof from the reaction mixture. No mention is made of a continuously operated process, however.
J. Am. Chem. Soc. 1998, 120, 9481 et seq. addresses the problem of producing soluble molecular weight enlargements, inter alia, for hydrogenation catalysts. Wandrey et al have also reported the use of a molecular weight-enlarged hydrogenation catalyst in a membrane reactor (Angew. Chem. (1990), 102, 445 et seq.). In this case, the desired substrate, NAD+, is symmetrically hydrogenated by the catalyst. Only thereafter does the asymmetric hydrogen transfer occur with the assistance of an alcohol dehydrogenase on the Cxe2x95x90O bond.
Hydrogenation processes proposed to date in the conventional processes operate discontinuously and/or require a mediator such as alcohol dehydrogenase. Thus, the above-described problems and others have not been adequately solved to date, and there is still a need for novel catalyst systems which make it possible to perform continuous processes catalytically.
Accordingly, one object of the present invention is to provide a continuously operating catalytic, asymmetric hydrogenation process.
Another object of the present invention is to provide a continuously operating catalytic and asymmetric hydrogenation process using molecular weight-enlarged catalysts.
Another object of the present invention is to provide a continuously operating catalytic and asymmetric hydrogenation process in which the product is easily separated from the reaction mixture.
Another object of the present invention is to provide a molecular weight-enlarged ligand for preparing such a catalyst.
Another object of the present invention is to provide a method for preparing such ligands and catalysts.
Another object of the present invention is to provide a homogeneous soluble hydrogenation catalyst that is readily separable from the hydrogenation product.
These and other objects have been achieved by the present invention, the first embodiment of which provides a process, which includes:
in a continuous process in a membrane reactor, asymmetrically hydrogenating at least one Cxe2x95x90C, Cxe2x95x90N or Cxe2x95x90O double bond with a molecular weight-enlarged catalyst.
Another embodiment of the present invention provides a ligand, which includes:
at least one di-1,3-aminophosphine homochiral active center;
optionally, a linker; and
a molecular weight-enlarging polymer;
wherein the active center is bound to the molecular weight-enlarging polymer through the linker or is bound directly to the molecular weight-enlarging polymer; and
wherein the linker is a member selected from the group including formulae (a)-(g):
wherein
R is H, (C1-C8) alkyl, (C6-C18) aryl, (C7-C19) aralkyl, or ((C1-C8) alkyl)1-3xe2x80x94(C6-C18) aryl;
X is (C6-C18) arylene, (C1-C8) alkylene, (C1-C8) alkenylene, ((C1-C8) alkyl)1-3xe2x80x94(C6-C18) arylene, or (C7-C19) aralkylene;
Z is C(xe2x95x90O)Oxe2x80x94, C(xe2x95x90O)NHxe2x80x94, C(xe2x95x90O)xe2x80x94, NR, O, CHR, CH2, Cxe2x95x90S, S, or PR; Z being bound directly to the molecular weight-enlarging polymer; and
W is C(xe2x95x90O)Oxe2x80x94, C(xe2x95x90O)NHxe2x80x94, C(xe2x95x90O)xe2x80x94, NR, O, CHR, CH2, Cxe2x95x90S, S, PR, W being bound directly to the active center.
Another embodiment of the present invention provides a process for preparing the above-noted ligand, which includes at least one step selected from the group including (a)-(c):
(a) binding the active center to a monomer directly or through a linker to provide a modified monomer, and polymerizing the modified monomer in the presence of one or more unmodified monomers;
(b) binding the active center to a polymer, either directly or through linker; and
(c) carrying out either of steps (a) or (b), and further polymerizing the resulting polymer with one or more additional polymers, wherein the one or more additional polymers optionally include one or more catalytically active centers.
Another embodiment of the invention provides a catalyst, that includes the above-noted ligand and one or more metals or metal ions selected from the group including Ru, Rh, Ir, Pd, Ni, Pt, Co, ions thereof, and mixtures thereof.